/*
 * $Header: /home/barad-dur/vision/forsyth/schenney/sced-0.94/c/RCS/triangle.c,v 1.2 1997/06/11 21:12:52 schenney Exp $
 *
 * $Log: triangle.c,v $
 * Revision 1.2  1997/06/11 21:12:52  schenney
 * Added vertex normal calculation function for control pt objects.
 *
 * Revision 1.0  1997/05/06 20:30:22  schenney
 * Initial revision
 *
 */
/*
**    ScEd: A Constraint Based Scene Editor.
**    Copyright (C) 1994-1998  Stephen Chenney (schenney@cs.berkeley.edu)
**
**    This program is free software; you can redistribute it and/or modify
**    it under the terms of the GNU General Public License as published by
**    the Free Software Foundation; either version 2 of the License, or
**    (at your option) any later version.
**
**    This program is distributed in the hope that it will be useful,
**    but WITHOUT ANY WARRANTY; without even the implied warranty of
**    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
**    GNU General Public License for more details.
**
**    You should have received a copy of the GNU General Public License
**    along with this program; if not, write to the Free Software
**    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include <math.h>
#include <sced.h>
#include <add_constraint.h>
#include <triangle.h>


static void
Triangle_Calculate_Vertices(ObjectInstancePtr obj, VectorPtr verts,
			    int num_real, int num)
{
    int	i;
    for ( i = 0 ; i < 3 ; i++ )
	verts[i] = control_part(obj)->control_verts[i];
    if ( i < num )
	VNew(0, 0, 0, verts[i]);
}


static void
Triangle_Calculate_Normal(ObjectInstancePtr obj, VectorPtr normal)
{
    Vector  temp_v1, temp_v2;
    double  temp_d;

    VSub(control_part(obj)->control_verts[2],
         control_part(obj)->control_verts[0], temp_v1);
    VSub(control_part(obj)->control_verts[1], 
         control_part(obj)->control_verts[0], temp_v2);
    VCross(temp_v1, temp_v2, *normal);
    if ( VZero(*normal) )
        VNew(1, 0, 0, *normal);
    else
        VUnit(*normal, temp_d, *normal);
}


static void
Triangle_Calculate_Vertex_Normal(ObjectInstancePtr obj, VectorPtr normal,
				 int num)
{
    Vector  temp_v1, temp_v2;
    double  temp_d;

    VSub(control_part(obj)->control_verts[2],
         control_part(obj)->control_verts[0], temp_v1);
    VSub(control_part(obj)->control_verts[1], 
         control_part(obj)->control_verts[0], temp_v2);
    VCross(temp_v1, temp_v2, *normal);
    if ( VZero(*normal) )
        VNew(1, 0, 0, *normal);
    else
        VUnit(*normal, temp_d, *normal);
}

void
Triangle_Create_Function(ObjectInstancePtr obj)
{
    Create_Generic_Object(obj);

    obj->o_hook = (void*)New(ControlHook, 1);
    control_part(obj)->num_control_verts = 3;
    control_part(obj)->control_verts = New(Vector, 3);
    VNew(0, 0, 0, control_part(obj)->control_verts[0]);
    VNew(0.5, M_SQRT1_2, 0, control_part(obj)->control_verts[1]);
    VNew(1, 0, 0, control_part(obj)->control_verts[2]);
    control_part(obj)->calc_verts = Triangle_Calculate_Vertices;
    control_part(obj)->calc_face_norms = Triangle_Calculate_Normal;
    control_part(obj)->calc_vert_norms = Triangle_Calculate_Vertex_Normal;

    /* Create the 3 extra features. */
    obj->o_num_features += 4;
    obj->o_features = More(obj->o_features, Feature, obj->o_num_features);

    Feature_Create_Dummy_Constraints(obj->o_features + tri_dummy_feature);
    Feature_Create_Control_Constraints(obj->o_features + tri0_feature, obj, 0);
    Feature_Create_Control_Constraints(obj->o_features + tri1_feature, obj, 1);
    Feature_Create_Control_Constraints(obj->o_features + tri2_feature, obj, 2);

    obj->o_static_func = Maintain_Control_Obj_Static;
    obj->o_dynamic_func = Maintain_Control_Obj_Dynamic;
}

void
Triangle_Destroy_Function(ObjectInstancePtr victim)
{
    free(control_part(victim)->control_verts);
    free(victim->o_hook);
    Destroy_Generic_Object(victim);
}

void
Triangle_Copy_Hook(ObjectInstancePtr src, ObjectInstancePtr dest)
{
    int i;

    ControlHookPtr  src_hook = (ControlHookPtr)src->o_hook;
    ControlHookPtr  dest_hook = (ControlHookPtr)dest->o_hook;

    for ( i = 0 ; i < 3 ; i++ )
        dest_hook->control_verts[i] = src_hook->control_verts[i];
}